The pair of apparent copycat knifings may have been inspired by an attack which left eight children dead at the end of March in a school in the eastern province of Fujian.

Parents across China are now panicking that a wave of killings, with their echoes of campus massacres in the United States, could be unleashed in a country where many families only have a single child.

Xu Xuyuan, a 47-year-old former insurance salesman who was fired from his job in 2001, broke into Taixing's Central Kindergarten just after nine o'clock on Thursday morning, after the children had completed their morning exercises and had filed into class.

Wielding an eight-inch blade, he powered past an elderly porter before locking himself inside a ground-floor first grade classroom in the school's south block. Only seven children out of the class of 37 managed to escape unharmed.

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Chen Xuefang, 36, said her three-year-old son had been slashed across his throat. "When I got to the school, the police told me I had to go to the hospital," she said.

"I rushed over and started searching through the wards. Finally I caught sight of him wearing his yellow sweater and being wheeled into a lift. I screamed out his name, and I think I saw his head move, but the doctor told me he was in a very serious condition. I do not know when I will see him."

Five of the children, all of whom were aged between three and four years old, were said by the authorities to be in a critical, but stable, condition.

Several sources in the city said that at least four children had died in the attack, but the Chinese authorities declined to comment.

Caijing, one of China's leading magazines, also reported the four casualties.

One mother, who spoke to the Daily Telegraph, said hospital officials had confirmed to her that some children had died and that the figures from the government did not tally. "There were 37 children in the class. Seven are safe and the government says that there are 28 in the hospital. Which leaves at least two unaccounted for," she said.

One eyewitness, who works in a shop in the alley next to the school, said she had rushed to the scene after hearing screams.

"I pushed into the building and I saw teachers carrying out wounded children. One girl had a deep gash in her head and her face was covered in blood. In the corridor I saw a teacher and a child lying motionless on the floor. I went into shock," she said, but declined to give her name.

Dai Xiamei, 43, said she had helped take some of the children to the hospital. "When I got to the kindergarten I saw a teacher carrying a child covered in blood. She was screaming out that crazy man was killing kids in the classroom. I helped take them both to the hospital and then went back to the school to help some more.

"I saw one little girl whose hand was nearly sliced off and took her to the hospital too. When I got there, there were eight or nine children being treated in the emergency ward, and one teacher lying on the floor. I thought the teacher must have been dead otherwise she would have been placed on a bed. Some of the injured kids in the school may not have made it to the hospital."

As night fell in Taixing, a crowd of around 200 people were still standing outside the kindergarten, with hundreds more gathering in a vigil outside the hospital. Inside the hospital, hundreds of relatives and friends had blocked corridors and clogged the lifts.

One 30-year-old man outside the kindergarten, who named himself only as Mr Cai, said: "I have a two-year-old boy. He was supposed to go to kindergarten next year. But we are terrified of what is going on. We will school him at home."

Another 62-year-old woman, who declined to be named, said: "What is wrong with this society that people are killing small kids? I live on this street and I used to see them every day. I nearly had a stroke when I heard what had happened this morning."

In a bid to calm the rising panic across the country, Chinese authorities censored posts from internet forums and National Security employees hushed residents in Taixing.

The motivation for the latest attack remains unclear, with some speculating that Mr Xu had been enraged by having his house repossessed by the government.

"There will be more killings if the social injustice and unfairness are not addressed," said one commenter on a forum at Xinhua, the government news agency, before Thursday's attack.

"The weaker seek revenge after they failed to get a response from society and failed to see any hope for protecting their rights."

Yu Jianrong, an expert on social unrest at the Chinese Academy of Social Sciences and an adviser to the very highest levels of the Communist Party, said the attacks should not be cast in the light of social justice but had spiralled out of individual cases of mental disorder. However, he warned that the cases could be "socially infectious", with other killers taking their cue from media reports.